This invention relates to a refractory lining within a foundry furnace for containing an iron melt having a silica slag, which lining is composed of mullite and corundum to resist corrosion by the slag. More particularly, this invention relates to a method for forming the lining that includes sintering a ramming mix composed of raw kyanite particles and alumina particles and produces compressive forces during sintering that strengthen the product lining.
In a typical coreless induction foundry furnace containing iron melt, the melt compartment is lined by a continuous refractory material. The lining is formed by positioning an expendable steel liner within the furnace about the compartment, but spaced apart from the furnace wall. An aggregate of dry, unbonded refractory particles, referred to as a ramming mix, is packed into the space about the steel liner. Iron melt is introduced into the compartment, whereupon heat from the melt sinters the ramming mix to form the refractory lining, and the steel liner is dissolved.
The furnace lining is typically composed of cristobalite, derived from a silica-base ramming mix. Malleable iron melt has a silica-base slag which corrodes a silica lining so that replacement is necessary. Refractory materials such as mullite or alumina resist attack by silica slag, but heretofore linings formed from ramming mixes of these materials have not developed sufficient sintered strength and tend to crack during use.
Therefore, it is an object of this invention to provide a method for forming a corrosion-resistant, crack-resistant mullite-corundum lining within a foundry furnace, such as a coreless induction furnace for containing malleable iron, which method employs an improved ramming mix comprising kyanite and alumina particles. The ramming mix is sinterable to produce a lining composed substantially of mullite and corundum to resist attack by silica slag. Furthermore, the ramming mix is formulated to develop significant compressive forces in the packed body during sintering that strengthen the product lining to prevent cracking. As a result, the useful life of the lining is extended.